Prior to the present invention, various platinum catalysts were available for effecting the addition of silicon hydride to vinyl-substituted silicon materials referred to as "hydrosilylation". For example, Karstedt, U.S. Pat. Nos. 3,715,334 and 3,775,452 assigned to the same assignee as the present invention, shows the use of Pt(O) complex with vinylsilicon siloxane ligands as an active hydrosilylation catalyst. Additional platinum complexes, such as complexes with platinum halides are shown by Ashby, U.S. Pat. No. 3,159,601 and Lamoreaux, U.S. Pat. No. 3,220,972, assigned to the same assignee as the present invention.
Another hydrosilylation catalyst is shown by Fish, U.S. Pat. No. 3,576,027. Fish prepares a platinum(IV) catalyst by reacting crystalline platinum(IV) chloroplatinic acid and organic silane or siloxane to form a stable reactive platinum hydrosilylation catalyst.
Although the aforementioned patents show that various platinum complexes are efficient hydrosilylation catalysts, additional platinum complexes providing improved hydrosilylation rates are constantly being sought.
The present invention is based on my discovery that a colloidal platinum complex in the form of a reaction product of a silicon hydride and an organic solvent solution of a platinum(O) complex or a platinum(II) complex, can provide superior hydrosilylation rates. I have found that in particular instances, optimum catalyst activity can be obtained, if the components of the reaction mixture are allowed to react for a time sufficient to provide a colloid having a red to a red-brown or black color.